Crystal Facet Dependence of Water Oxidation on BiVO4 Sheets under Visible Light Irradiation

Monoclinic BiVO4 crystals with preferentially exposed (040) facets were hydrothermally synthesized by using a trace amount of TiCl3 as the directing agent; this function was confirmed by X-ray diffraction patterns (XRD) and high-resolution transmission electron microscopy (HRTEM). The effects of the directing agent TiCl3 and the pH values applied during synthesis have been studied, and the optimized BiVO4 sample with highly exposed (040) facet could be obtained by using 1.2 at.% of TiCl3 as the directing agent at a pH value of 2. Some complementary techniques were also applied to exclude the effects of the structural and physical property changes, such as surface area and hydrophilicity. The photocatalytic activity of oxygen evolution on BiVO4 is found to be proportionally correlated with the exposed surfaces of the (040) facet. It is assumed that the active sites with a BiV4 structure on the exposed (040) facet is assigned to be responsible for the high activity of O-2 evolution.